The present invention relates to a driving tool for fastening fasteners, more particularly to a tool for electrically fastening or unfastening fasteners, such as the bolts used for mounting tires on an automobile.
Generally, fasteners, such as bolts, used for mounting tires on an automobile frequently become frozen in place, e.g., by rust, so that they are difficult to remove by conventional wrenches. This problem is particularly present when changing a vehicle tire if the tire bolts have not been removed for a long period of time. When this occurs, women or older and weaker persons are not able to unfasten the tire bolts because it is necessary to apply an extremely large force to the tire bolts in order to unfasten them. Various driving tools have been designed in order to resolve this problem, these driving tools are all driven by a power of motor.
In operation of these conventional driving tools, however, chattering occur with irregular and inaccurate hitting of a hammer since the engaging speed of the hammer and a connecting member is slow, the connecting member is for connecting the hammer to a spindle of which one end is provided with a wrench. Also, the chattering cause wear of parts in those driving tools and shortens their lifetime thereof.
An object of the present invention is to provide a driving tool for fastening fasteners of which a lifetime can be increased by regularly and accurately hitting a connecting member for connecting the hammer to a spindle and preventing chattering from generating therein.
Another object of the present invention is to provide a driving tool for fastening fasteners which can easily be used by women or older and weaker persons for mounting tires on an automobile.
These and other objects can be accomplished a driving tool for fastening fasteners according to one embodiment of the present invention which comprises a housing having a switch provided at a grip thereof and being divided into a part chamber in which parts are disposed and a motor chamber in which a motor is disposed; an inertial wheel being installed rotatably in the part chamber and engaged with a shaft of the motor; a spindle being installed rotatably between the part chamber and the inertial wheel and provided with a connecting member on an outer circumference thereof and a wrench on an end thereof; a hammer being pivotally installed at the inertial wheel to hit the connecting member by centrifugal force according to the rotation of the inertial wheel and returned to the initial position by a return spring positioned between the inertial wheel and the hammer; and means for accelerating instantaneously the pivoting motion of the hammer when the hammer is pivoted outwardly.
The hammer is preferably provided with a weighting member positioned at the rear portion thereof.
The weighting member has a weight against a spring force of the return spring such that the rear portion of the hammer can be pivoted outwardly when the inertial wheel is rotated.
The return spring has a loop shape to contain the rear portion of the inertial wheel.
The accelerating means includes a pair of balls contained in holes formed at both sides of the inertial wheel and arc shaped grooves formed at the hammer, respectively, springs for pressing the balls into the holes inwardly, respectively, and screws threaded to the holes for adjusting the pressing force of the balls by the springs, respectively.
The accelerating means may also includes an acceleration plate moving in the same direction as that of the hammer and having a recess for containing and supporting the rear portion of the hammer and an opening for containing the rear shaft of the inertia wheel, a cylindrical body engaged with the rear portion of the hammer and supporting the return spring, and a spring and a ball for accurately positioning the accelerating plate.
The spindle has a key groove at the outer side thereof, the connecting member has a hollow portion in the center thereof, the hollow portion has jaws formed at the inner surface thereof in a certain angle, a pair of springs are provided oppositely between the hollow portion and the spindle to absorb shock generated when the key engaged in the key groove is caught on one of jaws in both directions.
Alternatively, these and other objects can be accomplished a driving tool for fastening fasteners according to another embodiment of the present invention which comprise a housing having on-off switch provided at a grip thereof and being divided into a part chamber in which parts are disposed and a motor chamber in which a motor is disposed; an inertial wheel being installed rotatably in the part chamber and engaged with a shaft of the motor; a spindle being installed rotatably between the part chamber and the inertial wheel and provided with a connecting member on an outer circumference thereof and a wrench on an end thereof; a hammer being pivotally installed at the inertial wheel to hit the connecting member by centrifugal force according to the rotation of the inertial wheel and returned an initial position by a return spring positioned between the inertial wheel and the hammer; a hitting adjusting plate for gripping an upper portion of the hammer to accelerate instantaneously the pivoting motion of the hammer when the hammer is pivoted outwardly; and means for absorbing shock generated when the hammer hits the connecting member and provided between the spindle and the connecting member.
The hammering adjusting plate is directly connected with the hammer.
The means for absorbing shock is a pair of springs which are disposed oppositely between the spindle and the connecting member when the spindle is coupled with the connecting member.